黄顶菊入侵对土壤氨氧化细菌群落结构及多样性的影响

Effects of Flaveria bidentis invasion on soil ammonia-oxidizing bacterial community strucure and diversity

入侵植物通常会改变入侵地土壤微生物群落,进而影响到土壤养分循环以及物种之间的竞争格局。研究入侵植物对入侵地土壤微生物群落的影响不仅可以评估其对入侵地生态系统的影响,也为探明外来植物入侵的土壤微生物学机制提供理论依据。本文利用聚合酶链式反应变性梯度凝胶电泳(PCR-DGGE)技术及序列分析方法研究了入侵植物黄顶菊对入侵地土壤氨氧化细菌(AOB)多样性和系统发育的影响。结果表明:未入侵土壤(CK)、入侵地根围土(BS)和入侵地根际土(RPS)土壤AOB主要为亚硝化螺菌属(Nitrosospira sp.)、亚硝化弧菌属(Nitrosovibrio)、不可培养的亚硝化单胞菌属(Nitrosomonas)和不可培养的氨氧化细菌。其中,亚硝化螺菌群和不可培养的氨氧化细菌为各样地的优势类群。各样地AOB的Shannon指数(H)变化趋势为:RPS>CK>BS,土壤硝化潜势变化趋势与之一致,而影响H的关键理化因子分别是土壤硝态氮和铵态氮含量。黄顶菊入侵降低了BS的AOB活性,并表现出明显的根际效应,暗示黄顶菊可能通过加速自身根际氮素周转实现其成功入侵。

Invasive plants usually change invaded soil microbial communities which have an im- portant regulatory role in soil nutrient cycling and inter-species competition. Thus, it is important to investigate the effect of invasive plants on native soil microbial communities so as to assess their effect on native ecosystems and the microbial mechanisms involved. In this study, the effect of Flaveria bidentis, an invasive plant, on soil ammonia-oxidizing bacteria （AOB） community was investigated by using polymerase chain reaction-denaturing gradient gel electrophoresis （PCR-DGGE）. The results showed that most identified AOB were Nitrosospira sp. , Nitrosation vibrio, uncultured Nitrosomonas and uncultured AOB in the studied soils, with the domination of Nitrosospira and uncultured AOB. The Shannon indexes of AOB were in order of invaded rhizo- sphere soil 〉 non-invaded soil 〉 invaded bulk soil, and the soil potential nitrification rate fol- lowed the same pattern. Also, both nitrate and ammonium nitrogen contents were correlated closely with the Shannon index. It was concluded that AOB community diversity was reduced following the invasion of F. bidentis with the rhizosphere effect detected, suggesting that F. bidentis might promote its spreading by boosting N-cycling in rhizosphere in the invasion process.